The present application relates to a liquid crystal module and an electronic apparatus, and more particularly to a liquid crystal module in which a flexible printed wiring circuit (hereinafter referred to as “an FPC”) substrate for a light emitting diode (hereinafter referred to as “an LED”) as a backlight light source is electrically connected to an FPC substrate for a liquid crystal display panel, and an electronic apparatus using the same.
A liquid crystal display panel is used as a display panel in many electronic apparatuses because the liquid crystal display panel has the features such as light weight, slimness and low power consumption as compared with a Cathode Ray Tube (CRT). The liquid crystal display panel is such that an alignment of liquid crystal molecules arranged in a predetermined direction is changed by application of an electric field to change an amount of light transmitted through a liquid crystal layer, thereby displaying an image on the liquid crystal display panel. With regard to the light made incident to the liquid crystal layer, there are an outside light in a reflection type liquid crystal display panel, and a light emitted from a backlight light source in a transmission type liquid crystal display panel. The reflection type liquid crystal display panel has an advantage that electric power saving is obtained and visibility under a strong outside light is high. On the other hand, the reflection type liquid crystal display panel has an advantage that the visibility in a dark environment is high. In addition, a semi-transmission type liquid crystal display panel is also known which has the features of both the reflection type liquid crystal display panel, and the transmission type liquid crystal display panel.
Owing to the advantage that the visibility under the dark environment is high, almost the liquid crystal display panels are either of the transmission type or of the semi-transmission type. The transmission type or semi-transmission type liquid crystal display panel requires the backlight light source, and thus is manufactured in the form of a liquid crystal module in which a backlight unit is integrally mounted to the liquid crystal display panel.
With regard to the liquid crystal module, right under type and side light type are both known. Here, the right under type liquid crystal module is such that the backlight light source is disposed on a back surface of the liquid crystal display panel. Also, the side light type liquid crystal module is such that a light guiding plate is disposed on the back surface of the liquid crystal display panel, and the backlight light source is disposed on a side surface of the light guiding plate. In the side light type backlight light source, the light emitted from the light source is reflected in a direction of the liquid crystal display panel by the light guiding plate. For this reason, the side light type backlight light source has an advantage that the liquid crystal module can be made thinner in the side light type backlight light source than in the right under type backlight light source, and thus it is easy to uniformize the luminances.
In addition, a cold cathode discharge tube and an LED are used as the backlight light source in many cases. The LED has the following advantages. That is to say, the miniaturization is realized, the electric power consumption is less, and the long life is realized as compared with the case of the cold cathode discharge tube. Also, since mercury causing the environmental pollution is not contained in the LED and the direct current lighting is possible, the LED generates the less high frequency noises and is easy to lighten even at the low temperature. For this reason, the backlight light source composed of the LED is used in a middle-sized or small-sized portable electronic apparatus, especially, a mobile phone, a portable navigation system or the like in many cases. In addition, in recent years, for the purpose of making the best use of advantages that the LED has the less electric power consumption, can be thinned, and shows the high color rendering properties, the LED has come to be used in a large-sized liquid crystal display panel as well.
As shown in Japanese Patent Laid-Open Nos. 2006-018179 and 2008-226965 (referred to as Patent Document 1 and Patent Document 2 hereinafter, respectively) as well, the FPC substrate for an LED to which the LED as the backlight light source is mounted has a derivation portion extending to the outside in order to supply an electric power of a power source to the LED. Also, the derivation portion of the FPC substrate for an LED is electrically connected to an FPC substrate for a liquid crystal display panel for driving the liquid crystal display panel in some cases. In such cases, connection portions of the liquid crystal module can be assembled into one FPC substrate for a liquid crystal display panel. As shown in Patent Document 1 and Patent Document 2 as well, the FPC substrate for an LED is electrically connected to the FPC substrate for a liquid crystal display panel by an anisotropic conductive adhesive agent, soldering, connector connection or the like.
In this connection process, the workability and the bonding quality are both further enhanced in the case where the FPC substrate for a liquid crystal display panel is electrically connected to the FPC substrate for an LED in a state in which it extends planarly without being folded into an L letter-like shape than in any other case. The anisotropic conductive adhesive agent is obtained by mixing a thermosetting resin with fine metallic particles each having a conductive property. A pressure is applied to a part by using a butt having elasticity and heated by a heater or the like to apply a pressure only to the anisotropic conductive adhesive agent abutting against a convex portion of an electrode, thereby electrically connecting the FPC substrate for an LED to the FPC substrate for a liquid crystal display panel. As a result, a conductive path is formed while the conductive particles dispersed within the film contact one another. Since the anisotropic conductive adhesive agent requires the heating pressure bonding as described above, the bonding may be difficult to carry out unless the FPC substrate for a liquid crystal display panel planarly extends.